For many food products, moisture levels must be maintained if the product is to exhibit optimum organoleptic properties, quality, and taste. Moisture migration in finished food products can seriously compromise quality, stability, and organoleptic properties. In addition, many chemical and enzymatic deteriorative reactions proceed at rates partially governed by the moisture content of foods. Excessive rates of these reactions can promote deleterious changes in the flavor, color, texture, and nutritive value of food products.
In multi-component food products, particularly those having components with different moisture contents and water activities (e.g., prepackaged cheese and crackers or prepackaged bagel and cheese cream products), moisture can migrate between adjacent components and alter characteristics and organoleptic properties of the components. In addition to compromising the quality of finished food products, moisture migration can hinder production and distribution of food products. Thus, for example, the cheese in a cheese/cracker product could dry out while, at the same time, the cracker loses its crispness.
One method to prevent moisture migration in foods involves coating one or more surfaces of the food product with an edible moisture barrier. Such barriers should have a low moisture permeability in order to prevent the migration of water between areas of differing water activities. In addition, the barrier should cover the food surface completely, including crevices, and adhere well to the food product surface. The moisture barrier should be sufficiently strong, soft, and flexible to form a continuous surface that will not crack upon handling, yet can be easily penetrated during consumption. In addition, the barrier's organoleptic properties of taste, aftertaste, and mouthfeel should be imperceptible so that the consumer is not aware of the barrier when the food product is consumed. Finally, the moisture barrier should be easy to manufacture and easy to use.
Because lipids, such as oils, fats, and waxes, are composed of lipophilic water insoluble molecules capable of forming a water impervious structure, they have been investigated for use in moisture barrier films. With respect to oleaginous materials derived from lipids (i.e., sucrose polyesters, acetylated monoglycerides, and the like) and/or other film-forming lipids, it has been shown that, unless an undesirably thick coating is used, the barrier is not sufficiently effective for food products requiring long shelf life. Such film-forming lipids tend to become unstable under normal practical use conditions and lose film integrity and barrier effectiveness. In addition to structural instability, such as oiling out or cracking upon handling or with changes in temperatures, such lipid-based moisture barriers have disadvantages of being organoleptically unacceptable (e.g., greasy or waxy mouthfeel).
Accordingly, many of the barriers in the art use a water-impermeable lipid in association with hydrocolloids or polysaccharides such as alginate, pectin, carrageenan, cellulose derivatives, starch, starch hydrolysates, and/or gelatin to form gel structures or crosslinked semi-rigid matrixes to entrap and/or immobilize the nonaqueous or lipid material. In many cases these components are formed as bilayer films. These bilayer films may be precast and applied to a food surface as a self-supporting film with the lipid layer oriented toward the component with highest water activity. See, for example, U.S. Pat. No. 4,671,963 (Jun. 9, 1987); U.S. Pat. No. 4,880,646 (Nov. 14, 1987); U.S. Pat. No. 4,915,971 (Apr. 10, 1990); U.S. Pat. No. 5,130,151 (Jul. 14, 1992).
There are, however, a number of drawbacks associated with these moisture barriers. The hydrocolloids themselves are hydrophilic and/or water soluble and thus tend to absorb water with time. The absorption of water by the hydrophilic material in a moisture barrier is greatly accelerated while the film is directly in contact with foods having a water activity (Aw) above 0.75. In addition, some hydrocolloids tend to make the barriers fairly stiff, requiring the addition of a hydrophilic plasticizer (e.g., polyol) to increase flexibility. These plasticizers are often strong moisture binders themselves thus promoting moisture migration into the barriers and decreased structural stability and effectiveness of the barriers. Furthermore, the texture and the required thickness of some of these barriers may make their presence perceptible and objectionable when the product is consumed. Additional processing steps (casting and drying) required to form these films make them difficult to use in high speed commercial production.
U.S. Publication No. 2004/0101601 to Loh et al. and U.S. Publication No. 2004/0166204 to Smith et al. describe edible moisture barriers formed of a microparticulated high melting lipid (1-35 weight percent) and a low melting triglyceride blend (65-99 weight percent). These edible moisture barriers are supported by crystalline fat particles which help immobilize the liquid oil fraction in the barrier. The fat particles of the moisture barriers of these references initially crystallize in the alpha crystal form but this crystal form is lost by recrystallization to beta and beta prime morphologies.
The drawbacks related to the moisture barriers in the art include their caloric content and the presence of trans fats. Trans fats are known to raise LDL cholesterol levels, lower HDL cholesterol levels, and increase the risk for coronary heart disease. The FDA estimates that the average daily intake of trans fats per individual in the United States is about 5.3 grams or 2.6 percent of calories per day. (Food Labeling: Trans Fatty Acids in Nutrition Labeling, Nutrient Content Claims, and Health Claims, 68 Fed. Reg. 41,434, 41,444 (Jul. 11, 2003)). As of Jan. 1, 2006, the U.S. Food & Drug Administration required that trans fats be identified in the nutrition labels of all conventional foods and dietary supplements. Under FDA guidelines, for a food or fat to be listed as having zero trans-fatty acids, it has to contain less than about 0.5 grams of trans-fatty acids per serving. To achieve such levels in a typical baked snack food product, the trans-fatty acids in the particular ingredient oils must be kept well below about 3 to about 7 percent.
Edible, low calorie fat compositions based on mixtures of triglycerides having combinations of short and long chain fatty acid residues are known in the art. Salatrim (an acronym for “short- and long-chain acyl triglyceride molecules”) is a family of reduced calorie triacylglycerols comprising short chain and saturated long chain acid residues. Salatrim is prepared by interesterification of triacetin, tripropionin, or tributyrin, or their mixtures with either hydrogenated canola, soybean, cottonseed, or sunflower oil. Salatrim contains saturated long chain acids and short chain acids and typically contain 30-67 percent mole percent short chain fatty acids and 33-70 mole percent long chain fatty acids. It has further been found that these lipids exhibit stable alpha crystal habits. Salatrim is commercially available as BENEFAT® from Danisco A/S. See also, for example, U.S. Pat. No. 5,662,953 (Sep. 2, 1997) and U.S. Pat. No. 6,277,432 (Aug. 21, 2001). The '432 patent describes plastic fat compositions comprising a triglyceride mixture where the mixture contains 40 to 95 weight percent SSL and SLS species and 5 to 60 weight percent LLS and LSL species, and where 3 to 40 weight percent of the long chain fatty acid groups are unsaturated. The '953 patent describes triglyceride compositions comprising at least about 75 percent by weight SSL and SLS species and between 0.1 to 25 percent by weight LLS and LSL species, which can be coated on chocolate confections to reduce bloom.
Edible, low calorie fat compositions based on mixtures of triglycerides having combinations of short, medium, and long chain fatty acid residues are known in the art. See, for example, U.S. Pat. No. 5,380,544 (Mar. 5, 1993). These fat compositions are useful for incorporation into shortening and margarine products. The '544 patent describes fat compositions containing at least 24 percent, preferably at least 34 percent, and in some embodiments at least about 50 to 80 percent or higher of so-called “SML,” “SLM,” and “MSL” triglycerides bearing a short chain residue (S), a medium chain residue (M), and a saturated long chain residue (L). Preferred methods maximize the isolation of “SML,” “SLM,” and “MSL” triglycerides by removing “SSS,” “SSM,” “MMS,” “MSM,” “MMM,” “SSL,” and “SLS” species from the reaction mixture.
The edible moisture barriers provided by the present invention represent a significant improvement over prior art moisture barriers and overcome the problems associated with the prior art moisture barriers. The edible moisture barriers of the present invention have reduced caloric value, are essentially free of trans-unsaturated fatty acids, contain a significant concentration of triacylglycerols that have melting points below ambient temperature and crystallize in stable alpha-crystal morphologies, and have improved moisture barrier properties over the barriers in the prior art.